Narrowly distributed emulsifier-free cationic polymethylmethacrylate latex particles were prepared by using microwave irradiation in the presence of initiator 2

2′-azobis isobutyramidine dihydrochloride．The effects of initiator concentration

monomer concentration

ionic strength and heating method on the size

shape and stability of latex particles were discussed．Results showed that the average particle size increased with increasing the monomer concentration and ionic strength．The stability of latex had similar tendency of chage．However

it initially decreased with the increase of the initiator concentration

passed through a minimum

and then increased．In comparison with the conventional heating method

using microwave irradiation increased reaction rate and number of particles

and decreased particle diameter．No constant rate stage existed in the reaction．The method presented here is useful to prepare other type of latex particles.